Fabrication Of Two-dimensional Ti₃C₂T_x MXene Membrane And Electro-enhanced Performance In Water Treatment

Membrane separation technology has been widely used in water treatment due to the advantages such as operation at room temperature operation,no secondary pollution and so on,and the preparation of high-performance separation membranes is becoming more and more important.New two-dimensional materials especially MXene provides conditions for fabricating high-performance separation membrane due to its strong hydrophilic and controlled layer spacing.Nowadays,the research on improving rejection of MXene membrane focuses on methods of crosslinking and intercalation,leading to lower permeability duo to reduction of layer spacing.Meanwhile,there is less research on the mitigation of MXene membrane fouling and membrane regeneration,in order to explore these issues,taking advantage of MXene’s high electrical conductivity,MXene（Ti₃C₂T_x）electrochemical separation membrane is prepared in this study.By enhancing electrostatic repulsion,membrane rejection rate is improved while maintaining membrane flux and the membrane pollution is alleviated.At the same time,membrane regeneration is realized through electrochemical cleaning.The main research contents and conclusions are as follows:（1）The MXene membrane with a thickness of about 50 nm is prepared after regulating the properties of the membrane in this study.Negative voltage is applied to the MXene membrane to promote rejection rate of negatively charged pollutants by enhancing electrostatic repulsion,and its mechanism is also explored.The results show that the application of-2V to the membrane universally enhances the rejection rates for dyes（MO,OG,BCG,CR）,anionic surfactants（SDS,SDBS）,antibiotics（AS,PGP）and humic acid.Taking antibiotics as an example,with-2 V voltage applied,the membrane can maintain a pure water flux of 28.0L/（m²·h·bar）,while the rejection rates of ampicillin sodium and penicillin potassium are increased to 45.9%and 78.1%,5.7 times and 7.0 times that of without voltage,respectively.The mechanism research shows that application of negative electricity improves the charge density on the membrane surface,and enhances electrostatic repulsion between membrane and pollutant molecules,thus promoting rejection rates of pollutants.（2）Humic acid is used to simulate natural organics and an electrochemical assisted membrane separation system is constructed,in which negative voltage is applied to the MXene membrane,taking advantage of MXene’s high conductivity,to alleviate membrane fouling in the process of separating humic acid with a concentration of 50 mg/L and regenerate the polluted membrane,and its mechanism is also explored.The results show that membrane fouling is alleviated with the-2 V voltage applied,that the stable normalized membrane flux increases to 64.5%,1.40 times that of without voltage.Applying-3 V voltage on the polluted MXene membrane can effectively clean and regenerate the membrane,and flux recovery rate reaches more than 92%with-3 V voltage applied,not damaging the membrane structure at the same time.The mechanism investigation shows that under a low voltage（-2 V cell voltage）,the electrostatic repulsion is enhanced,which increases the Donnan effect between membrane and humic acid,alleviating the membrane fouling;whereas under a high voltage（-3 V cell voltage）,enhanced electrostatic repulsion and the hydrogen evolution reaction work together,therefore quickly realizing in-situ membrane regeneration.